Railway track circuit apparatus



April 12, 1938. R. M. GlLSON 2,113,982

RAILWAY TRACK CIRCUIT APPARATUS Filed Feb.-28, l936 2 Sheets-Sheet l 5 F 5: 1 a 24 Y 20 )2 i Lia: {Ia I A A Ta n 0 5a Tb r 0 A g F491 B 6 Slowpzbli 'up 4 i 2 :I /S (la Tla T111 13 4 A A my 3 Slow Pz'ol up V 24 7 32a )2 7 L345 (Ia t Ta Tb INVENTOR ZZ sum HIS ATTORN EY Patented Apr. 12, 1938 UNITED STATES PATENT OFFICE 2,113,982 RAILWAY TRACK CIRCUIT APPARATUS Robert M. Gilson, Pittsburgh, Pa., assignor to The Union Switch & Signal Company, Swiss- 11 Claims.

My invention relates to railway track circuit apparatus, and has for an object the provision of novel and improved means for increasing the shunting sensitivity of apparatus. of this character.

1 I will describe several forms of track circuit apparatus embodying my invention, and will then point out the novel features thereof in claims.

The present application is a continuation-inpart of my copending application, Serial No. 737,249, filed. July 27, 1934, for Railway track circuit'apparatus, in so far as the subject matter common to the two cases is. concerned.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing one form of direct current track circuit apparatus embodying my invention. Fig. 2 is a diagrammatic view showing one form of alternating current track circuit apparatus embodying my invention. Fig. 3 is a 20 diagrammatic view showing a modification of Fig. 1, also embodying my invention. Figs. 4 and 5 are diagrammatic views showing modified'forms of the apparatus ofv Fig. 2, and also embodying my invention. Fig. 6 is a diagrammatic view showing a modification of a portion of Fig. 5.

Similar reference characters refer to similar parts in each of the views.

Referring first to Fig.- 1, the reference characters l and la designate thetrack rails of a stretch of railway track, which rails are divided by insulated joints 2 to form a track section EG. At least one of the rails is divided by an insulated joint 2a at an intermediate point in this section to provide two sub-sections EF and. F--G. As shown in the drawings, each rail I and la is provided with an insulated joint 2a at the point F. A trackbattery 3 is connected around the joint 2a in rail l, alimiting-impedance 4 being interposed between one terminal of the battery and is connected around the joint 2a in rail la, a limiting-impedance 4a being interposed between one terminal of this battery and the rail of section F-G. The two batteries 3 and 3a are oppositely poled, so that if rail I of section EF is positive, rail Ia of section F-G is also positive. A direct current track relay Ta is connected across the rails of the section EG adjacent the lefthand end of the section, and a similar track relay Tb is connected across. the rails adjacent the right-hand end of the section. A relay A is provided with a circuit which passes from terminal B of a suitable source of current, through a 5 front contact 51) of relay Tb, a front contact 5a of the rail of section EF. A similar battery 3a relay Ta, and the operating winding of relay A to terminal 0 of the same source of current. I

If the two subsections E-F and F-G are equal in length, then the ballast resistance of these two subsections will be approximately equal, and this approximate equality will be maintained regardless of variations in weather conditions. This being so, the two limiting-impedances 4 and 4a will be adjusted to the same values which they would have if the two sub-sections EF and F--G were provided with standardtrack circuits.

For a clearer understanding of the required magnitude of the limiting resistors 4 and 4a as wellas of the voltage oi sources 3 and 3a, it is advantageous to consider that the two track circuits of section EG normally operate independently of each other. That is, the track relay Ta, for example, is energized only from the source 3 through the resistor 4-, and the track relay Tb is energized only from its respective source 3a through the resistor 40.. When the track circuits are analyzed in this manner, it becomesimmediately apparent, in view of the fact that the two track circuits are of substan tially equal length and have track relays of similar characteristics associated therewith, that the values of the limiting resistors 4 and 40. for equal voltages at sources 3 and 3a will also be equal. That is, since the track circuits of sections EF and FG normally operate as though independent of each other the constants of these track circuits will be the same as for standard track circuits of equal length, equipped with similar track relays.

The relay A may be utilized to control traffic governing apparatus of any suitable type. As here shown, the section E--G is provided with a signal S the circuit for which is controlled by a front contact 6 of relay A.

When a train moving toward the right enters subsection EF, the wheels and axles will form a shunt around the terminals of the operating winding of relay Ta, and the effectiveness of this shunt will be high, because the multiple resistance of relay Tb and the resistance of the ballast in subsection F--G will be in series with batteries 3 and 3a. That, is, whatever current reaches relay Ta under the shunted condition must pass not only through the usual battery limiting resistor 4 but also partly through the windingof relay Tb and partly through the ballast resistance of sub-section FG. Accordingly, the voltage remaining across relay Ta under the shunted condition will be much lower :1

due to this added resistance, and the shunting effectiveness will be much higher than in the case of the usual track circuit in which the track relay current during the shunting operation is limited by the battery resistor only. The higher the ballast resistance, the greater will be the value of this additional resistance in the track circuit. In dry weather-when the usual track-circuit. is most difiicult to shunt, no path will exist through the ballast of sub-section F-G and the full resistance of the winding of relay Tb will there; fore be effective in limiting the flow of current in relay Ta during the shuntingoperations It will be seen, therefore, that the apparatus provides, self-compensation to prevent excessiye oveifenergization of the relays in dry weather atthe time that the sections are shunted. the train passes out of sub-section E-F"andinto"sub section FG, track relay Tb will be shunted; and.

track relay Ta will become energized. Relay A will become deenergized as soon asrelay Ta releases, a'ndwill'remain deenergized aslong as the train occupies any part of section'EG When alight car passes-throughthesection at high speed, relay Ta may 'bec'omeenergized before rel'ayfTb 'relea-sesg' Relay A'is preferably slow 'pickupin character toprevent momentary clearing of'signal S under thiscondition.

Referring now to-rg. Zgthe apparatus shown in this view is the-same as'that shown-in Fig. 1', except that the batteries are replaced by secondaries 8' and 8a of a transformer D, the primary 1 of which is constantly supplied with al-,

ternating current from a source not shownin the drawings. The track'relays, which are here designated. Tl-a and TH respectively, are, of course, of the alternating current type instead of the direct current type used with theapparatus shown in Fig; 1. *The operation and characteristics of the apparatus shown in Fig. 2 are the same as those of the apparatus shown in The apparatus shown in either Fig-xi oriFig. 2 may be modified by-omitting-ene of the-insulated joints 2a and the associated source oi track circuit current. Fig. 3 shows such a-modi'ficati'on of Fig. 1. This modification doe's not provide for equal ground potential for the two sub sea tions, resultstherefore in increased ballast leakage current in wet weather, thus requiring" a lower value of total limiting impedance which results in somewhat less sensitive; shunting. When a train enters section the current in relay Ta. will be limited not only: by-resis tor-d but also. by an additional resistance consisting ofthe winding of relay: Tb and'the ballast of f subsection F'G-,.Iin multiple, whereby improved shunting:v sensitivity over the usual track: circuit will be obtained. 'Ihererna-ining operation of the apparatus of Fig; 3 will-be clear from the foregoing description oi Fig-l. I 1

- Referring now to. Fig. 4, the. apparatus of this figure is identical with that of Fig.2, except that the limiting resistors; t and. 3a arereplaced by suitable rectifier units R and Ra which may, for example, be of the copper oxidetype. This per-- mits, the. use of direct. current track relays and a has thejadvantage over. a battery-fed .track circuit suchas shown in l; or Fig.3, in thatthepeak voltage; during an impulse .of current supplied. to the track through the rectifiers R andv muchhigher. than the effective voltage supplied from a track battery; Since. the. effectiveness of the train. shuntdepends, among other- The source of current is the battery 3, and this is periodically pole-changed'at any suitable rate, such, for example, as 60 operations per minute, by means of the constantly operating flasher or coding device C. The track voltageoutput of windings 8 and 3a.- will be in the form of short impulses of relatively high peak value, thus aiding to improve the shunting sensitivity for substantiallythe same reasons as in Fig. 4. The a1- ternating current track relays Tia. and Tlb of Fig. 5- can be of either the steadily energized or code-following type, as desired, depending upon the type of wayside signal control'which is used. Instead of steadily energized alternating current relays, direct current relays plus rectifiers can also be used. This modification of Fig. 5 is shown in Fig. 6.. The operation of the D. C.

'rely-rectifiercombination of Fig.- 6 will be clear without added description. 7

The principal advantage of apparatus embodyi-ng my inventionlies in its. provision for automatic variation in the shunting sensitivity of the track circuit in response to variations in ballast resistances. As a result of this characteristic it ispossible, by proper selection-of relays and batteries, to obtain as good or better shunting under dry weather conditions as is obtained under wet. weather conditions. If the track relays shown in. the drawings are. replaced by what is known as. the primary-secondary track relay combination, the resulting. apparatus will have from two to three times the minimum shunting sensitivity of thestandard track circuit with the primary-secondary relay combination under the mostunfavorable weather conditions. Moreover, by makingv use of. the peak voltage apparatus of'Figs. 4 and 5, more reliable shunting can be obtained in conjunction with track sections hav ing an'appreciablei rail film resistance.

' Although I have herein shown and described only a. few forms of apparatus embodying my in vention, it is understood that. various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention,

claim is:

. 1. In combination, a section of railway track divided by insulated rail joints each rail at an; intermediate. point, two track relays connected across'the rails adjacent the two ends of said sectionrespectively; two oppositely poled sources of track circuit current connected across said two joints respectively and exclusive of .any electrical connection from one to said other source other than the rails of said section, whereby when a train enters said section the winding of the track relay at the leaving end of said section will be included in a series circuit with said. two sources to thereby limit the track voltage at the entering what I end of said section to facilitate release of the.

2. In combination, a section of railway track divided by insulated rail joints in each rail at an intermediate point, two track relays connected across the rails adjacent the two ends of said section respectively, and two oppositely poled sources of track circuit current connected across said two joints respectively and exclusive of any electrical connection from one to said other source other than the rails of said section, whereby when a train enters said section the winding of the track relay at the leaving end of said section will be included in a series circuit with said two sources to thereby limit the track voltage at the entering end of said section to facilitate release of the track relay at said entering end.

3. In combination, a section of railway track divided by insulated rail joints in each rail at an intermediate point, two track relays connected across the rails adjacent the two ends of said section respectively, two oppositely poled sources of track circuit current connected across said two joints respectively and exclusive of any electrical connection from one to said other source other than the rails of said section, and a current limiting impedance inserted in the connection between a terminal of one of said sources and the associated rail.

4. In combination, a section of railway track I divided by insulated rail joints in each rail at an intermediate point, two alternating current track relays receiving energy from the rails adjacent the two ends of said section respectively, and two oppositely poled sources of alternating track circuit current connected across said two joints respectively and exclusive of any electrical connection from one to said other source other than the rails of said section, whereby when a train enters said section the winding of the track rea lay at the leaving end of said section will be included in a series circuit with said two sources to thereby limit the track voltage at the entering end of said section to facilitate release of the track relay at said entering end.

5. In combination, a section of railway track divided by an insulated rail joint in one rail at an intermediate point in the section, two track relays connected across the rails adjacent the two ends of said section respectively, and a single source of track circuit current for said section connected across said rail joint for maintaining both of said track relays picked up from said single source.

6. In combination, a section of railway track divided by an insulated rail joint in one rail at an intermediate point in the section, two track relays receiving energy from the rails adjacent the two ends of said section respectively, and a source of track circuit current connected across said rail joint and exclusive of any electrical connection from said source to the remaining rail of said section except through said two track relays.

7. In combination, a section of railway track divided by an insulated rail joint in one rail at an intermediate point in the section, two track relays receiving energy from the rails adjacent the two ends of said section respectively, a transformer having an output winding connected across said rail joint, said output winding being exclusive of any electrical connection with the remaining rail of said section except through said two track relays, a source of direct current, and means including a coding device for supplying current from said source to the input winding of said transformer.

8. In combination, a section of railway track divided by insulated rail joints in each rail at an intermediate point, two alternating current track relays receiving energy from the rails adjacent the two ends of said section respectively, a transformer having two output windings connected across said two rail joints respectively with instantaneous polarities so chosen that said two windings aid one another in causing current to flow in the rails of said section, said two output windings being exclusive of any electrical connection therebetween other than the rails of said section, a source of direct current, and means including a coding device for supplying current from said source to the input winding of said transformer.

9. In combination, a section of railway track divided by an insulated rail joint in one rail at an intermediate point in the section, two track relays connected across the rails adjacent the two ends of said section respectively, a single source of track circuit current connected across said rail joint for maintaining both of said track relays picked up from said single source, and traific governing apparatus controlled jointly by said two track relays.

10. In combination, a section of railway track divided by an insulated rail joint in one rail at an intermediate point in the section, two track relays connected across the rails adjacent the two ends of said section respectively, a rectifier, and a source of alternating track circuit current for said section connected across sail rail joint through said rectifier and exclusive of any electrical connection from said source to the remaining rail of said section except through said two track relays.

11. In combination, a section of railway track divided by an insulated rail joint in one rail at an intermediate point in the section, two track relays connected across the rails adjacent the two ends of said section respectively, a copper oxide rectifier, and a source of alternating track circuit current for said section connected across said rail joint through said rectifier and exclusive of any electrical connection from said source to the remaining rail of said section except through said two track relays.

ROBERT M. GILSON. 

